(#126) testing: `axEventBus` injection available to widget controllers during testing

Conflicts:
	CHANGELOG.md
Merge branch 'feature-0.20.x/126-testing-add-event-bus-injection-to-testbed' into release-0.20.x

* feature-0.20.x/126-testing-add-event-bus-injection-to-testbed:
  (#126) testing: `axEventBus` injection available to widget controllers during testing
release v0.20.1